The present invention relates to a power transmission chain having link plates which have protrusions or projections for maintaining a space between the guide link and the inside links.
One aspect of the invention relates to a silent or rocker joint chain which has links having inverted teeth for engagement with an associated sprocket. Generally, rocker joint chains are used with sprockets for power transmission in transmissions, transfer cases, engine timing systems, and the like. Rocker joint chains are well known in the art. Examples include U.S. Pat. Nos. 5,651,746; 5,345,753; and 5,372,554 which are incorporated herein by reference.
Rocker joint chains are formed by the assembly of rows of links in lateral and longitudinal directions. Each link typically has a pair of teeth and a pair of pin apertures. The links are interlaced and then connected to each other by connecting pins inserted in each pin aperture. Guide links are utilized as the outermost links of the chain to maintain the chain on the sprockets when the chain is wrapped around the sprockets during operation. Guide links may be installed in the center or at both outer edges of the row of link plates arranged in the lateral direction. The guide links are conventionally press fit over pins, which connect the interlaced inside or articulating links. Guide links typically do not include inverted teeth.
Conventionally, a rocker joint is used as the connecting pin. The rocker joint is comprised of a pair of long and short pins. A first short pin, referred to as the rocker, is paired with a second longer pin. The longer pin has both ends fixed to guide links at the outmost flanks of the chain.
Conventional rocker joint chains are limited in the transfer of load between the rocker and the inside links that are positioned at the outermost end of the rocker. The limitation is due to the fact that only partial contact is obtained between these same inside links and the end of the rocker. A separate limitation concerns the contact between the outermost inside links and the sprocket. Due to the required chamfer on sprocket teeth and the axial clearance between the sprocket teeth and chain guide links only partial contact is achieved between the same inside links and the sprocket.
A prior art rocker joint chain showing the disadvantage in conventional chain designs is shown in FIGS. 1-3. The chain is comprised of rows of links. Alternate rows of links, or guide rows, have guide links press fit on their ends. The remaining rows, or non-guide rows, have inside links as their outermost links.
FIG. 1 shows a prior art rocker joint chain in a side view. Rows of inner links 21 in a guide row 12 alternately interleave with rows of inner links 21 in a non-guide row 14 and held by rocker joints comprising pairs of pins 16 and rockers 18. A guide link 20 is fixed to the each end of the guide row 12 of inner links 21 by pins 16 which extend outwardly from the rows of inside links.
In the prior art rocker joint chain 10, shown in FIG. 2, there is a clearance 30 between the end of the rocker 18 and the guide link 20. This clearance 30 exists because of necessary manufacturing tolerances of the individual rockers 18 so that they are spaced from the guide links 20 after the assembly process. There also exists an end radius 19 on the rocker 18, which is necessary to prevent excessive local stresses in the pin 16 and rocker 18, and also for ease of assembly of the chain 10. The clearance between the rocker 18 and the guide link 20 and the shortening of the rocker as a result of the end radius of the rocker, result in only partial bearing contact between the outermost inside links 22, 23 of the non-guide row, and the rocker. The partial bearing contact limits the load carrying capability of the chain because all of the links are not carrying their full share of the load.
FIG. 3 shows an exaggerated cross section through the chain of the prior art and sprocket 40. The chain 10 is shown slightly out of position, i.e., raised vertically. The limitation in this design is that the contact area between the outermost inside links 22, 23 and sprocket tooth 25 is limited due to the chamfer 26 on the sprocket teeth and the necessary axial clearance between the chain 10 and sprocket 40. Thus, the partial engagement or partial contact occurs between the outermost inside links 22, 23 of the non-guide row and the sprocket.
The present invention also has application to silent chains with round connecting pins. An example of a round pin silent chain is shown in U.S. Pat. No. 4,758,209, which is incorporated herein by reference.
The present invention also has application to chain belts, as shown in U.S. Pat. Nos. 4,580,999 and 5,439,423 which are incorporated herein by reference.
The present invention addresses the above-described problems by providing in a power transmission chain, in general terms, a spacing element to space the guide links apart from the inside links. In one embodiment, this allows for increased rocker length and provides improved inside link-to-rocker contact. Also, the present invention allows increased sprocket width providing better contact between the chain and sprocket.
The present invention is applied to a power transmission chain having a plurality of interleaved link rows arranged into non-guide rows and guide rows. Each link plate includes a pair of apertures. The links are connected by pins inserted through the apertures. The chain is provided with a plurality of spacing elements which include, but are not limited to protrusions, washers, spacers, bumps, curved portions or elements, raised elements, or stops for spacing the guide links apart from the inside links. The spacing elements may be integral to links of the chain or may be separate elements.
In a preferred embodiment, the power transmission chain of the present invention includes guide links with spacing elements located on an inner surface of each guide link plate for maintaining a space between the main body of the guide link and the inside links. The spacing element is a projection and may be formed, for example, by pressing or stamping a recess or dimple on the outside of the guide link causing a corresponding raised element or rounded projection to form on the inside surface of the guide, link. The raised element or projection on the guide link bears upon an outside surface of the adjacent inside link and maintains a space between the main body of the guide link and the inside link.
The guide link of one embodiment of the present invention as applied to a rocker chain has projections formed on an inner face of the guide link which act to space the guide link away from the adjacent inside links. Spacing the guide link from the inside links permits a longer rocker that is fully within the outermost inside link and provides complete bearing contact between the rocker and the inside links, specifically the outermost inside links. The stress in the rocker is reduced by virtue of a slight increase in rocker length, and by keeping the inside link load away from the end of the rocker, reducing stress concentrations.
Another aspect of the present invention relates to silent chains which use a round cylindrical pin to connect link rows. The benefit of spacing members to a round pin silent chain is directed to the increase in contact area between the inside links and an associated sprocket.
Still another aspect of the present invention is related to chain type belts. The benefit of spacing members to a chain type belt is directed to the increase in contact area between the rocker pin and the outermost inside link aperture.
It should be understood that the number of projections provided each guide link includes one projection to many projections. In one preferred embodiment, four rounded projections are located on the inside face of each guide link. One pair of projections are spaced apart near the bottom edge of the guide link and the remaining pair are spaced apart near the top edge of the guide link. The spaced relationship of the four projections reduces the tendency of the adjacent inside link to rock or tilt.
In another embodiment, the present invention includes guide links which are spaced apart from the inside links by washers. The washers are located about the connecting pins between the guide links and the inside links and serve to space the guide links from the inside links.
In another embodiment, the present invention includes guide links with curved elements formed on the ends of the guide link which curve inwardly toward and bear upon the inside links. The curved end elements give the guide link a xe2x80x9cCxe2x80x9d or xe2x80x9cUxe2x80x9d shape as viewed from above as opposed to the typical flat plate form of the prior art.
In another embodiment, the present invention includes guide links with curved spacing elements formed in the middle portion of the link. The curved mid-elements or portions cause the guide link to exhibit a non-flat shape and acts to maintain a space between the guide links and the inside links.
For a better understanding of these and other aspects and objects of the invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings.